Grazia Careccia

Hepatitis C Virus Genotype Analysis in Patients with Type II Mixed Cryoglobulinemia

Hepatitis C virus (HCV) infection has been related to different autoimmune-lymphoproliferative diseases such as autoimmune hepatitis [1, 2] and mixed cryoglobulinemia [3, 4]. The latter condition is associated with HCV infection in almost 90% of cases and is characterized by symptoms of systemic vasculitis secondary to deposition of coldprecipitable immune complexes. The remote pathogenesis of mixed cryoglobulinemia is considered to be a B-cell lymphoproliferation, which in many patients can be complicated by malignant lymphoma [5, 6]. Because of the variability of the HCV genome, one might speculate that particular viral variants are responsible for mixed cryoglobulinemia. Thus, we assessed the prevalence of different genotypes in HCV-positive cryoglobulinemic patients and in patients with chronic HCV infection who did not have cryoglobulinemia. Methods From March 1994 to September 1994, we recruited (at ambulatory visits) 29 consecutive HCV-positive (anti-HCV antibody-positive and HCV RNA-positive) patients with type II (IgM ) mixed cryoglobulinemia (9 men, 20 women; mean age SD, 60 7.5 years; age range, 46 to 72 years) and 61 patients with chronic HCV infection who did not have mixed cryoglobulinemia (control group). All patients studied were Italian-born, were heterosexual, and had no history of blood transfusion or drug or alcohol abuse. Cryoglobulinemic and control patients were followed at the rheumatology and hepatology units of the University of Pisa and University of Florence. The mean (SD) duration of follow-up was 8.4 5.5 years (range, 1 to 25 years) for cryoglobulinemic patients and 6.8 4.5 years (range, 2 to 14 years) for controls. A diagnosis of mixed cryoglobulinemia was made if a patient had the typical syndrome (purpura, arthralgias, weakness, and circulating mixed cryoglobulins) and if other well-known systemic disorders could be ruled out. Eight cryoglobulinemic patients developed B-cell non-Hodgkin lymphoma 4.3 2.7 years (range, 1.5 to 8 years) after diagnosis. After informed consent was obtained, percutaneous liver and renal biopsies were done as previously described [4, 7]. Cryocrit determinations were done and cryoglobulin composition was evaluated as previously described [4, 8]. Antinuclear, anti-smooth muscle, anti-liver-kidney microsomal 1, anti-soluble liver antigen, and antimitochondrial autoantibodies were assayed by current techniques [9]. A titer greater than 1:40 was considered positive. Anti-extractable nuclear antigen antibody determinations were done using the method of Bunn and colleagues [10]. Serum samples and aliquots of peripheral blood mononuclear cells with the last washing liquid (phosphate-buffered saline) for HCV polymerase chain reaction (PCR) analysis were collected as previously described [11, 12]. In addition, to ascertain the presence of a latent HCV infection, peripheral blood mononuclear cell samples were cultured for 72 hours in the presence of mitogens (phytohemagglutinin-phorbol myristate acetate) as previously described [11, 12]. Different samples were tested by one-tube nested reverse transcriptase PCR with primers derived from the 5 noncoding region [13]. Several precautions were taken to prevent false-positive results [14], including the incorporation of deoxyuridane-triphosphate instead of deoxythymidine-triphosphate during amplification steps followed by incubation of PCR mixtures for 3 minutes at 50 C in the presence of uracil-N-glycosilase (UNG; Perkin Elmer Cetus, Norwalk, Connecticut). In nine unselected patients with mixed cryoglobulinemia, aliquots of peripheral blood mononuclear cells were also available for HCV genotyping. Hepatitis C virus genotyping was done using two different methods, both based on amplification by PCR. The first technique used type-specific primers localized in the core region, as described by Okamoto and colleagues [15], with the difference that PCR was done without mixing genotype-specific antisense primers. Moreover, for the detection of genotype III, we used a new primer that, in a previous study, made it possible to classify most previously unclassified HCV isolates as genotype 2a/III [16]: This primer was CRIIIa antisense 5-TTCCCCAGGAYT TGCCAGTGG-3 (Y equals C or T). The second one employed biotinyled, universal primers localized in the 5 noncoding region of HCV RNA; amplification products were then hybridized to genotype-specific probes (Line Probe Assay, LiPA, Innogenetics, Brussels, Belgium). Statistical analysis was done using the chi-square test and the Fisher exact test whenever the z approximation was inadequate. Results Table 1 shows the values for the main clinicoepidemiologic and laboratory variables in patients with mixed cryoglobulinemia. The following complications of mixed cryoglobulinemia were recorded: peripheral neuropathy in 15 of 29 patients (52%); mild sicca syndrome in 11 of 28 (39%); glomerulonephritis in 4 of 29 (13%); Raynaud phenomenon in 1 of 28 (4%); and skin ulcers in 3 of 28 (11%). One or more serum autoantibodies were detected in 8 of 28 (29%) patients with mixed cryoglobulinemia and in 19 of 61 (31%) controls. Table 1. Clinico-epidemiologic Data and Laboratory Findings in 29 Hepatitis C Virus RNA-Positive Patients with Mixed Cryoglobulinemia* Hepatitis C virus RNA sequences were shown in uncultured peripheral blood mononuclear cells from 23 of 29 (75%) patients with mixed cryoglobulinemia and in cultured cells from 3 other patients (total, 90%) (Table 1). In the control group, viral sequences were detected in uncultured or mitogenstimulated peripheral blood mononuclear cells from 46 of 61 (75%) and 49 of 61 persons (total, 80%), respectively (Table 1). Among the 29 patients with mixed cryoglobulinemia, serum specimens showed a single infection with type 1a/I in 1 patient (3 %), with type 1b/II in 14 patients (48%), and with type 2a/III in 12 patients (41%). Two patients (6.6%) had mixed infection (1a/I plus 1b/II and 1b/II plus 2a/III, respectively) (Table 1). Among the 61 controls, genotypes 1a/I, 1b/II, 2a/III, 3a/V, and 4a were observed in 7 (11%), 37 (61%), 9 (15%), 4 (7%), and 1 (1%) patient, respectively, whereas mixed infection (1a/I plus 1b/II; 1b/II plus 2a/III; 1b/II plus 3a/V) was observed in 3 (5%) patients. When HCV genotypes detected in peripheral blood mononuclear cells were also considered, type 2a/III was found in 15 of the 29 (52%) patients with mixed cryoglobulinemia and in most autoantibody-positive patients (6 of 8; 75%) (Table 1). The prevalence of 2a/III genotype was significantly higher in patients with mixed cryoglobulinemia (12 of 29; 41%) than in controls (9 of 61; 15%), a difference of 27 percentage points (95% CI, 6.6% to 46.6%; P = 0.009). No other significant differences were observed between the two groups. Sixteen of the 29 patients with mixed cryoglobulinemia had chronic aminotransferase elevations. Analysis of serum samples showed that 12 of these patients (75%) were infected with HCV genotype 1b/II and that 4 (25%) were infected with HCV genotype 2a/III (Table 1). Of the remaining 13 patients who showed no clinical evidence of liver damage, 8 (61%) had infection with genotype 2a/III, 3 (23%) had infection with genotype 1b/II, 1 (7%) had infection with genotype 1a/I, and 1 had coinfection with types 1b/II and 2a/III. Liver biopsy, done in 14 patients, showed chronic hepatitis in 13 patients and liver cirrhosis in 1 patient; 2 patients with chronic hepatitis and 1 patient with cirrhosis had persistently normal aminotransferase levels (Table 1). Among the 61 controls, 27 (44%) had chronic hepatitis, 21 (34%) had liver cirrhosis, and 13 (21%) had hepatocellular carcinoma; none had normal aminotransferase values. Discussion In our study, HCV genotype 2a/III had a significantly higher prevalence in HCV-positive patients with mixed cryoglobulinemia than in patients with chronic hepatitis who did not have cryoglobulinemia. Among cryoglobulinemic patients, this genotype was more frequent in those without a symptomatic liver disease or with circulating autoantibodies. Recently, several reports have suggested different clinical outcomes for the HCV genotypes. Type 1b/II infection, for example, has been associated with a more severe liver disease and a lower response to interferon treatment, whereas type 2a/III infection has been considered relatively benign [17-19]. This hypothesis is consistent with the observation that genotype 2a/III is more prevalent in cryoglobulinemic patients without symptomatic liver disease than in those with chronic hepatitis. On the other hand, the higher prevalence of genotype 2a/III in patients with mixed cryoglobulinemia than in controls, especially in cryoglobulinemic patients with circulating autoantibodies, suggests that type 2a/III might be involved in the pathogenesis of autoimmune-lymphoproliferative disorders. The recent observation that type 2a/III is particularly frequent in Italian patients with anti-liver-kidney microsomal 1 autoantibody-positive type 2 autoimmune hepatitis further supports the possibility of a peculiar pathogenetic role for this genotype [20]. A recent study [8] showed that patients with mixed cryoglobulinemia have a high prevalence (81%) of HCV infection in peripheral blood mononuclear cells, suggesting that HCV lymphotropism may play a key role in determining the lymphoproliferative disorder underlying the disease. Our study confirms these data and also shows the frequent infection of lymphatic cells in HCV-positive patients with chronic hepatitis who do not have cryoglobulinemia. We can thus hypothesize that different viral, genetic, or environmental factors, in addition to the infection of lymphatic cells, may be involved in the pathogenesis of this disorder. The exact role of HCV variants, namely 2a/III, which are possibly related to different host immune reactivity or to a greater lymphotropism, should be clarified through deeper virologic analysis, including examination of lymph-node and bone

Hepatitis C virus infection in mixed cryoglobulinemia and B-cell non-Hodgkin’s lymphoma: evidence for a pathogenetic role

SummaryWe investigated the pathogenetic relevance of hepatitis C virus (HCV) infection in mixed cryoglobulinemia (MC) with or without complicating B-cell Non-Hodgkin’s lymphoma (NHL) in comparison with other immunological and lymphoproliferative disorders. The following groups of patients were studied: A) 25 patients with MC in 7 cases evolved into B-cell NHL; B) 25 healthy subjects; C) 22 patients with different systemic immune diseases; D) 24 patients with chronic HCV infection without MC; E) 25 patients with B-cell idiopathic NHL. Methods used included: i) Polymerase chain reaction (PCR) for HCV RNA detection in serum and peripheral blood mononuclear cells (PBMC) (uncultured or mitogen-stimulated); ii) Branched DNA (b-DNA) for HCV RNA quantification; iii) HCV genotyping by genotype-specific primers localized in the core region and by hybridization of amplification products of the 5′ untranslated region (5′UTR), obtained with universal primers, using genotype-specific probes. Serum anti-HCV and HCV RNA were detected in 88% and 73% of MC patients, respectively, and in a significantly lower percentage of healthy controls and patients with autoimmune diseases. HCV RNA concentration was significantly lower in supernatants than in corresponding whole sera (p<0.001). Plus-strand HCV RNA was detected in 81% of peripheral blood mononuclear cell (PBMC) samples and minus-strand in the majority of fresh or mitogen stimulated cells. All MC patients with NHL had HCV RNA sequences in PBMC. HCV genotype 2a/III was detected in MC patients with a prevalence that was significantly higher than in HCV infected patients without MC. Surprisingly, HCV markers (anti-HCV and/or HCV RNA) were found in 32% of patients with idiopathic NHL. These data suggest that HCV infection is involved in the pathogenesis of MC through both direct participation in the immune complex related vasculitis and by triggering the lymphoproliferative disorder underlying the disease. This latter disorder seems to be related to HCV lymphotropism which could also be responsible for the evolution of MC to malignant lymphoma. This study also suggests that HCV infection may be involved in the pathogenesis of idiopathic B-cell NHL through a similar pathogenetic mechanism.

Hepatitis C virus infection in non‐Hodgkin's B‐cell lymphoma complicating mixed cryoglobulinaemia

The so-called essential mixed cryoglobulinaemia (MC) is an immune-mediated disorder characterized by the clinical triad-purpura, arthralgias and weakness-, and by various organ involvements, i.e. chronic hepatitis, glomerulonephritis, peripheral neuropathy, and generalized vasculitis [ 1,2]. The presence of a monoclonal rheumatoid factor in the cryoprecipitates [l], a clonal expansion of IgMk-bearing B cell in peripheral blood [3], lymphoid aggregates in bone marrow, spleen, or liver biopsies raised the possibility that MC is the expression of a low-grade malignant lymphoma [3-51. A striking association between hepatitis C virus (HCV) infection and MC has been demonstrated by various authors worldwide [6-81. The possible pathogenetic role of HCV was recently reinforced by the demonstration of viral genomic sequences in both sera and peripheral lymphocytes of MC patients [9]. HCV lymphotropism indicates that MC should be regarded as a primarily systemic lymphoproliferative disorder other than a simple extrahepatic manifestation of HCV-related chronic hepatitis. This hypothesis is further supported by the absence in 20-30% of MC patients of chronic hepatitis and more interestingly by the appearance in some subjects, generally after a long follow-up period, of a frank non-Hodgkins lymphoma (NHL). The evolution of MC to a malignant lymphoma can affect the overall prognosis of the disease. This study aimed to investigate the role of HCV infection in a series of B-cell NHL complicating MC.

Relevance of inapparent coinfection by hepatitis B virus in alpha interferon-treated patients with hepatitis C virus chronic hepatitis.

The aim of the study was to investigate whether an “inapparent” coinfection by hepatitis B virus (HBV) in anti‐HCV‐positive chronic liver disease patients may influence interferon (IFN) response. Fourteen anti‐HCV‐positive, hepatitis B surface antigen (HBsAg)‐negative but serum HBV‐DNA‐positive patients and 111 anti‐HCV‐positive, HBsAg‐negative, and HBV‐DNA‐negative patients with chronic hepatitis were treated with 3 MU of recombinant α‐2a IFN 3/week for 1.2 months. Serum HBV‐DNA and HCV‐RNA were determined before treatment, after 6–12 months, and at the time of alanine aminotransferase (ALT) flare‐up by HBV polymerase chain reaction (PCR) and HCV PCR, respectively. IgM anti‐HBc were tested using the IMx Core‐M assay (Abbott Laboratories, North Chigago, IL). By the end of treatment, ALT values had become normal in 4/14 HBV‐DNA‐positive patients (28%), but all “responders” (4/4) relapsed. IgM anti‐HBc was detected both before treatment and during ALT elevation in three patients and only during ALT relapse in another three. In the remaining 111 patients, a biochemical response to IFN treatment was observed in 54% and relapse of ALT values in 47%. “Inapparent” HBV/HCV coinfection may be implicated in cases of resistance to IFN. HBV replication and HBV‐related liver damage may persist in patients in whom HCV replication was inhibited by current doses of IFN, as suggested also by the presence of IgM anti‐HBc in some cases. Further studies will show the effect of different treatment schedules. HBV‐DNA and/or IgM anti‐HBc detection with very sensitive methods may be important both as a prognostic factor and as a tool for better understanding of intervirus relationships and mechanisms involved in multiple hepatitis virus infections. J. Med. Virol. 51:313–318, 1997.

Hepatitis C virus-related autoimmunity in patients with porphyria cutanea tarda.

Abstract. Hepatitis C virus (HCV) infection is frequently found in autoimmune hepatitis and mixed cryoglobulinaemia. In these conditions HCV could be responsible for immuno‐mediated organ alterations. The aim of this study was to evaluate the presence of immunological alterations in PCT patients, in which HCV infection has been frequently found. Twenty‐three PCT patients were evaluated for clinical and serological alterations, including: chronic hepatitis, other systemic symptoms, serum cryoglobulins and rheumatoid factor (RF), haemolytic complement, serum immunoglobulins, anti‐nuclear (ANA), anti‐smooth muscle (ASMA), anti‐liver‐kidney‐microso‐mal (anti‐LKMl), anti‐soluble‐liver‐antigen (SLA), anti‐mitochondrial (AMA), anti‐GOR antibodies, anti‐HCV and HCV RNA. Abnormal serum ALT were present in the majority of cases (20/23, 87%), while liver biopsy revealed a chronic persistent hepatitis or chronic active hepatitis in 15/20 (75%) PCT patients. In a high percentage of subjects (91%) the presence of anti‐HCV was detected by ELISA and RIBA II (Chiron, Emeryville CA, USA). In 17/22 (77%) cases the ongoing HCV replication in the serum was demonstrated by the detection of HCV genomes (polymerase chain reaction). The prevalence of both anti‐HCV and HCV RNA in PCT was significantly higher if compared to 22 systemic immunological diseases (P< 0.00l) and 47 healthy subjects (P<0.001). A possible HCV‐induced autoimmunity in PCT was suggested by the presence of the following immunological parameter alterations: anti‐GOR in 13/23 (57%), ANA in 4/23 (17%), ASMA in 18/23 (78%), anti‐LKMI in 1/23 (4%), RFin 23/23 (100%), mixed cryoglobulins in 4/23 (170/0), complement consumption in 10/23 (43%). The high prevalence of HCV infection and various immunological abnormalities suggest that HCV in combination with other factors (genetic, alcohol, etc.) could play a relevant role in the pathogenesis of hepatic and metabolic alterations of PCT.

Prevalence of mixed infection by different hepatitis C virus genotypes in patients with hepatitis C virus–related chronic liver disease☆☆☆★

Multiple infection by different hepatitis C virus (HCV) genotypes may be of great clinico-pathologic interest. In this study we determined the effective prevalence of coinfections by two or more HCV genotypes in 213 subjects with HCV-positive chronic hepatitis by using genotype-specific polymerase chain reaction (PCR), genotype-specific probe hybridization, and direct sequencing. The most prevalent genotype was HCV-1b (54%). HCV-2 (a/c) was also prevalent (27%), and types 1a and 3a were found in 5% and 3% of patients, respectively. A mixed infection was detected in 23 patients (10.8%): 4 out of 23 were coinfected by types 1a + 1b, while the remaining 19 patients had a b + 2 (a/c) mixed infection. Further analysis based on restriction fragment length polymorphism (RFLP) on type-specific PCR products was used to verify genotyping results. Only four coinfections (1a + 1b in 2 patients and 1b + 2 (a/c) in the remaining 2 patients, respectively) were confirmed by enzyme cleavage. All patients with true coinfection had long-lasting infection and liver cirrhosis. Both true and false mixed infections resulting from RFLP analysis were confirmed by direct sequencing of type-specific amplification products. We also determined a recurrent C/T transversion at position 618 in all sequenced samples. In 4 cases another point mutation (G/A at position 626) was found, reducing the number of mismatches between HCV-2 and HCV-1b from 4 to 3 (or 2). Interestingly, all HCV-2 isolates sequenced showed the highest degree of nucleotide homology with HCV-2 subtype c, confirming the relatively high prevalence of this subtype in Italy. In conclusion, we showed the possibility of multiple infection by different HCV types in the general population of chronically infected patients without particular risk factors, even if in a low percentage of cases. Further studies are needed to assess the clinical relevance of chronic HCV infection with multiple genotypes.

Impaired response to alpha interferon in patients with an inapparent hepatitis B and hepatitis C virus coinfection

SummaryThe possibility of hepatitis B virus (HBV) infection in HBsAg-negative patients has been shown. However, an “inapparent” coinfection by HBV in hepatitis C virus (HCV)-positive patients generally is not taken into account in clinical practice. Mechanisms responsible for resistance to interferon (IFN) have not been completely clarified. The aim of this study was to investigate whether an “inapparent” coinfection by HBV in anti-HCV-positive chronic liver disease patients may influence IFN response. Fourteen anti-HCV positive, HBsAg-negative but serum HBV DNA-positive patients by PCR and 111 anti-HCV-positive, HBsAg-negative and HBV DNA (PCR)-negative patients with chronic hepatitis were treated with 3 MU of recombinant α-2a IFN 3 times weekly for 12 months. Serum HBV DNA and HCV RNA were determined before treatment, after 6–12 months and in coincidence with ALT flare-up by PCR. HBV PCR was performed using primers specific for the S region of the HBV genome and HCV PCR with primers localised in the 5′NC region of HCV genome. IgM anti-HBc was tested using IMx Core-M Abbott assay. By the end of treatment, ALT values had become normal in 4/14 HBV DNA-positive patients (28%), but all “responders” (4/4) relapsed between 2 and 5 months after therapy. All but one patient were HCV RNA-positive before treatment, 6 were also both HBV DNA and HCV RNA-positive during ALT flare-ups. In 5 patients, only HBV DNA and in 3 patients, only HCV RNA was detected when transaminase values increased. All patients remained HBsAg-negative and anti-HCV-positive. IgM anti-HBc was detected both before treatment and during ALT elevation in 3 patients and only during ALT relapse in 3 others. Of the 111 anti-HCV positive, HBsAg-negative and HBV DNA (PCR)-negative patients with chronic hepatitis, a biochemical response to IFN treatment was observed in 54% of the cases. Relapse of ALT values was observed in 47% of the cases during a follow-up of 1 year after treatment. “Inapparent” HBV/HCV coinfection may be implicated in cases of resistance to IFN treatment. In addition, HBV replication may persist in patients in whom HCV replication was inhibited by IFN treatment. The pathogenic role of HBV in liver disease was confirmed by detection of IgM anti-HBc in some cases; the appearance of these antibodies only after IFN treatment suggests that IFN may exert a selective role in favour of HBV. Further studies will show the effect of different treatment schedules. HBV DNA and/or IgM anti-HBc detection with very sensitive methods may be important both as a prognostic factor and as a tool for better understanding interviral relationships and mechanisms involved in multiple hepatitis virus infections.

Serum HCV-RNA and Liver Histologic Findings in Patients with Long-Term Normal Transaminases

In this study we aimed to correlate liverhistology and the presence of hepatitis C virus (HCV)viremia, genotype, and quantity of HCV genome in 19positive and 11 RIBA II indeterminate patientspresenting persistently normal ALT values over 24 monthsbefore biopsy. In addition, after biopsy serum ALTvalues were monitored monthly for a mean follow-upperiod of 24.8 months, after which patients werereevaluated for RIBA II and the presence of viremia.Sixteen patients (53%) were serum HCV-RNA-positive; 13of them (68%) were confirmed positive and 3 (27%)indeterminate on RIBA II. Histology of the HCV-RNA-positive patients showed eight cases of CPH (one case ofgenotype 1a; four cases type 1b; three cases type 2),six cases of CAH (three cases type 1b, three cases type2), one case of CLH (type not determined), and one case of normal liver (NL) (type 1b).Histology of the HCV-RNA-negative patients showed fourcases of CPH, one case of CAH, two cases of CLH, andseven cases of NL. During the follow-up period ninepatients (30%) presented slight increases in ALT values(<2 × N), and in particular, flares of ALT wereobserved four times in the CAH and five times in the CPHpatients, who were all viremic, but never in the NL subjects. These results indicate that subjectspositive on RIBA II, but with persistently normal ALTvalues, had a high probability of being serumHCV-RNA-positive and that almost all these viremicsubjects presented histologic signs of liver disease. Incontrast, RIBA II indeterminate subjects had a moderateprobability of being HCV-RNA-positive, but a number ofthese may present signs of liver disease. In both cases there was no association withgenotype or HCV-RNA serum levels. The other nonviremiccases included subjects with hepatic changes goingtoward resolution or with normal liver in whom hepatic biopsy can be avoided. Only one case was a truecarrier since he was viremic with normal liver andpersistently normal ALT values.

Lymphotropic Virus Infection of Peripheral Blood Mononuclear Cells in B-Cell Non-Hodgkin’s Lymphoma

Some lymphotropic viruses such as Epstein-Barr virus (EBV) and human herpesvirus 6 (HHV-6) have been proposed as causative agents of B cell non-Hodgkins lymphoma (NHL). More recently, the presence of hepatitis C virus (HCV), which is both a hepatotropic and lymphotropic virus, has been reported in one third of B cell NHL patients. The aim of this study was to investigate in a series of B cell NHL the prevalence of three lymphotropic viruses, i.e. EBV, HHV-6 and HCV, in peripheral blood mononuclear cells (PBMC). Eighteen unselected B cell NHL patients (10 men, 8 women; mean age 62 +/- 12 years, range 31-77 years; mean disease duration 1.8 +/- 1.4 years) and 40 age- and sex-matched healthy controls were included in the study. In all cases, an acquired-immunodeficiency-syndrome-related lymphoma was excluded. By means of the polymerase chain reaction technique, EBV DNA, HHV-6 DNA and HCV RNA were detected in PBMC. HCV genomic sequences were significantly more frequent in PBMC of NHL patients than in controls (33 vs. 2.5%; p < 0.01); on the other hand, in the same two groups EBV DNA (39 vs. 60%; p = not significant) and HHV-6 DNA (22 vs. 32%; p = not significant) were present in a comparable percentage of individuals in the same two groups. The infection of PBMC by HCV alone was present in the majority (5 of 6) of HCV-positive NHL. These data support the implication of HCV infection in a statistically significant number of B cell NHL, whereas a possible co-operation between HCV and other well-known lymphotropic viruses seems to be excluded.

Hepatitis C Virus Lymphotropism and Possible Pathogenetic Implications.

Hepatitis C virus (HCV) is a virus that contains a single-stranded positive-sense RNA genome and is distantly related to the flaviviruses and pestiviruses. Following its discovery, the identification at a structural level of existing analogies between HCV and Pesti- and Flavivirus, has become a basis for research in evaluating whether common aspects in the natural history of such infections exist. One of these analogies is the possibility to infect elements of the lymphatic system (lymphotropism). This viral characteristic is of interest in regards to possible clinical and pathological consequences. In particular, one of the most intringuing hypotheses concerns the possibility that HCV lymphotropism may represent at least one of the “missing links” between HCV infection and some lymphoproliferative disorders frequently observed in association with this infection. Studies performed in this field are in agreement with this hypothesis. However the direct demonstration is still lacking and clarification of the mechanisms eventually in play deserves further study.